According to statistics published by the National Transportation Safety Board, as many as 10 severe decompressions occur each year with U.S. air carrier operations and 1,500 to 2,000 passengers may be exposed to the dangers of decompression. Supplemental oxygen systems are provided to minimize these dangers. In Safety Recommendations dated Apr. 29, 1976, the National Transportation Safety Board discussed various alleged problems with chemically generated passenger supplemental oxygen systems. Among their Class III. (Longer-Term Follow Up) recommendations was "Develop standards for the use of accepted human factors, engineering principles and system design concepts in the design of passenger supplemental oxygen systems." That report, in discussing one specific prior art supplemental oxygen system, observed: "The system requires excessive passenger involvement and responses. The passenger must remove the oxygen mask from stowage, activate the system and use it properly." The report also noted that in three decompression incidents involving such a prior art system, passengers failed to pull the mask to their faces (such action was required to activate the system); instead, they leaned forward and attempted to breathe into the mask without fully removing it from the stowed position. In such a prior art system, a pin must be pulled from a spring loaded striker in order to initiate the oxygen generating process within the solid state oxygen generator; the pin is attached to the oxygen mask by a lanyard. Thus, when a sufficient pulling force is applied to the mask by the passenger, this force is transmitted by the lanyard to the pin, thereby causing the pin to be extracted from the striker mechanism. A similar lanyard and pin mechanism is utilized in other types of prior art oxygen systems wherein the oxygen is stored as a pressurized gas within a suitable pressure vessel and the pin is associated with a valve mechanism such that upon the extraction of the pin, a valve in the flow path between the source of the oxygen and the mask is opened.
In another type of prior art supplemental oxygen system, solid state oxygen generators are activated by means of an electric current which ignites a pyrotechnic fuse. In such systems, it is conventional to utilize the same electrical signal to activate the generation of the oxygen and to cause the oxygen masks attached to the oxygen generator to be presented to the passengers for use. Thus, no specific action is required by the passenger to initiate the flow of oxygen or otherwise to cause the deployment of the system. All that the passenger need do is place the mask through which the oxygen is already flowing into position against his nose and mouth. However, such electrically activated systems are expensive both in terms of cost and weight; furthermore, since all of the supplemental oxygen masks within the airplane are deployed and all of the associated oxygen generators are fired in response to a single electrical signal originating from a single sensing device (or from a single control switch aboard the flight deck), it is not practical for the deployment capabilities of the system to be tested during routine maintenance operations without the generators themselves being fired. Furthermore, in the event that the control switch is accidentally depressed, all the masks will be deployed and all the oxygen generators will be fired, requiring that each individual solid state oxygen generator be replaced and each individual mask be re-sanitized and carefully replaced in its stowed position inside its individual emergency compartment.
Thus, it will be appreciated that there is a need for an improved deployment system for emergency supplemental oxygen which during actual emergency conditions the individual passenger will find convenient and easy to use without elaborate instructions or assistance from the cabin crew and in which the proper operation and functioning of the electro-mechanical components can be conveniently tested without affecting the proper functioning of the individual components during a subsequent emergency and without requiring any subsequent labor intensive and costly sanitizing, repackaging and/or replacing of the masks or generators.